Tyler Shumway of Aurora, Colorado, lights up a joint at 420pm in Civic Center Park on 20 April 2012 in Denver.
Photograph: Marc Piscotty/Getty Images

Today may be the day that marijuana officially loses its cool. April 20, 4/20, the once underground national holiday for dope smokers, appears to have sold out to The Man.

The origins of 4/20 are as disputed as the last pack of gummy bears after a long smoking session. Some say it was once police code for “marijuana smoking in progress” – apparently untrue – and others claim it was invented by high school stoners in Marin county, California, who would meet at 4.20pm to get high.

No matter what the origins it’s big business for a rapidly growing industry – the Black Friday of getting high.

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This year’s 4/20 falls on a Saturday and is expected to be the biggest sales day yet for legal marijuana, exceeding an 111% sales spike record last year. Stoners will gather at Denver’s Civic Center Park to celebrate, with clouds of marijuana smoke drifting over the crowds, some still in tie-dye and preaching cosmic one-ness.

4/20 doesn’t have a Hallmark card yet but it can’t be far off. Of the hundreds of tie-in promotions this year, Lyft is offering a $4.20 credit on a single ride in Colorado and in select cities in the US and Canada. The fast-food chain Carl’s Jr is using a Denver outlet to test a hamburger infused with CBD oil.

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But there is a serious side to it. This year the ice-cream maker Ben & Jerry’s is calling on consumers to pressure lawmakers to expunge prior marijuana convictions for anyone arrested for smoking pot. Considering those arrests are four times more likely to affect African Americans, the social justice implications are clear.

According to Kit Yarrow, a consumer psychologist at Golden Gate University, 4/20 is on its way to becoming a mainstream national holiday and that’s largely a function of the booming marijuana business. Arcview, a cannabis investment and market research firm, estimates US retail sales of cannabis products jumped to $10.5bn last year, a threefold increase from 2017.

“It’s still a celebration of marijuana but the conversation has been expanded by brands that tie into the cannabis industry and for marketers to tie into something that has a coolness to it,” Yarrow says. That conversation, she adds, is increasingly focused on people wondering what role cannabis may play in their life.

“The stoner dude mentality is still there but there is another that is more focused on marijuana’s medicinal properties and that’s growing in stature,” said Yarrow.

The marijuana business could soon be dwarfed by the market for products using CBD, a cannabis compound from the hemp plant that supposedly has health benefits but doesn’t get you high.

CBD, which is not listed as a controlled substance, can now be found in candies, coffee and other food, drinks and dietary supplements, along with perfume, lotions, creams and soap.

According to Louis Zerobnick, a veteran Colorado cannabis promoter, the CBD industry has the potential to become a far larger business than an industry based on THC, the psychoactive ingredient in cannabis. As it is, he says, the marijuana industry has moved far beyond its hippie-stoner roots and is increasingly dominated by big industry and big banking.

“A lot of the old hippies aren’t going to make it in this new industry. Although they’re responsible for it, and did the activism to make it happen, you find that marijuana companies want to bring in people who have worked in other government-regulated industries. That’s the level of professionalism that’s now required to turn it into a real business,” said Zerobnick.

Zerobnick thinks 4/20 could one day exceed the size of other semi-official holidays, including Valentine’s Day and Halloween. “It’s a national, non-denominational, non-racial holiday mostly celebrated by getting high,” Zerobnick said, reeling off events scheduled in Florida, Chicago and the High Times’ Cannabis Cup in California. “For people who use cannabis 4/20 is as big as Christmas.”

And in the meantime Big Business is moving in to harsh the original stoners’ buzz. John Boehner, the permatanned former Republican speaker of the House, is a director of one of the US’s largest cannabis businesses, Acreage Holdings. Coca-Cola has joint venture with a cannabis company that could lead to Coke High. Big tobacco is waiting in the wings.

The 4/20 the counterculture pioneers who campaigned for legalization may well be wondering if there is a high price for a legal high.

“We don’t necessarily like it but everybody knows it,” says Zerobnick. At the same time that a lot of old hippies won’t make it, he says, “many could become billionaires when they’re bought out and their strains turned into commercial success”.